HDFS-4351.  In BlockPlacementPolicyDefault.chooseTarget(..), numOfReplicas needs to be updated when avoiding stale nodes.  Contributed by Andrew Wang


git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/branches/branch-1@1429655 13f79535-47bb-0310-9956-ffa450edef68